Reimplement the linked list data structure used throughout the backend.

In the past, we used a 'Lispy' linked list implementation: a "list" was
merely a pointer to the head node of the list. The problem with that
design is that it makes lappend() and length() linear time. This patch
fixes that problem (and others) by maintaining a count of the list
length and a pointer to the tail node along with each head node pointer.
A "list" is now a pointer to a structure containing some meta-data
about the list; the head and tail pointers in that structure refer
to ListCell structures that maintain the actual linked list of nodes.

The function names of the list API have also been changed to, I hope,
be more logically consistent. By default, the old function names are
still available; they will be disabled-by-default once the rest of
the tree has been updated to use the new API names.

1 files changed, 79 insertions, 71 deletions

diff --git a/src/backend/utils/adt/ruleutils.c b/src/backend/utils/adt/ruleutils.c
index 95e457c261f..213dc61202b 100644
--- a/src/backend/utils/adt/ruleutils.c
+++ b/src/backend/utils/adt/ruleutils.c
@@ -3,7 +3,7 @@
  *				back to source text
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/backend/utils/adt/ruleutils.c,v 1.166 2004/05/10 22:44:46 tgl Exp $
+ *	  $PostgreSQL: pgsql/src/backend/utils/adt/ruleutils.c,v 1.167 2004/05/26 04:41:38 neilc Exp $
  *
  *	  This software is copyrighted by Jan Wieck - Hamburg.
  *
@@ -627,6 +627,7 @@ pg_get_indexdef_worker(Oid indexrelid, int colno, int prettyFlags)
 	Form_pg_class idxrelrec;
 	Form_pg_am	amrec;
 	List	   *indexprs;
+	ListCell   *indexpr_item;
 	List	   *context;
 	Oid			indrelid;
 	int			keyno;
@@ -691,6 +692,8 @@ pg_get_indexdef_worker(Oid indexrelid, int colno, int prettyFlags)
 	else
 		indexprs = NIL;
 
+	indexpr_item = list_head(indexprs);
+
 	context = deparse_context_for(get_rel_name(indrelid), indrelid);
 
 	/*
@@ -733,10 +736,10 @@ pg_get_indexdef_worker(Oid indexrelid, int colno, int prettyFlags)
 			/* expressional index */
 			Node	   *indexkey;
 
-			if (indexprs == NIL)
+			if (indexpr_item == NULL)
 				elog(ERROR, "too few entries in indexprs list");
-			indexkey = (Node *) lfirst(indexprs);
-			indexprs = lnext(indexprs);
+			indexkey = (Node *) lfirst(indexpr_item);
+			indexpr_item = lnext(indexpr_item);
 			/* Deparse */
 			str = deparse_expression_pretty(indexkey, context, false, false,
 											prettyFlags, 0);
@@ -1358,7 +1361,7 @@ deparse_context_for_subplan(const char *name, List *tlist,
 	List	   *attrs = NIL;
 	int			nattrs = 0;
 	int			rtablelength = length(rtable);
-	List	   *tl;
+	ListCell   *tl;
 	char		buf[32];
 
 	foreach(tl, tlist)
@@ -1526,7 +1529,7 @@ make_ruledef(StringInfo buf, HeapTuple ruletup, TupleDesc rulettc,
 		 * (which can only be references to OLD and NEW).  Use the rtable
 		 * of the first query in the action list for this purpose.
 		 */
-		query = (Query *) lfirst(actions);
+		query = (Query *) linitial(actions);
 
 		/*
 		 * If the action is INSERT...SELECT, OLD/NEW have been pushed down
@@ -1556,7 +1559,7 @@ make_ruledef(StringInfo buf, HeapTuple ruletup, TupleDesc rulettc,
 	/* Finally the rules actions */
 	if (length(actions) > 1)
 	{
-		List	   *action;
+		ListCell   *action;
 		Query	   *query;
 
 		appendStringInfo(buf, "(");
@@ -1579,7 +1582,7 @@ make_ruledef(StringInfo buf, HeapTuple ruletup, TupleDesc rulettc,
 	{
 		Query	   *query;
 
-		query = (Query *) lfirst(actions);
+		query = (Query *) linitial(actions);
 		get_query_def(query, buf, NIL, NULL, prettyFlags, 0);
 		appendStringInfo(buf, ";");
 	}
@@ -1636,7 +1639,7 @@ make_viewdef(StringInfo buf, HeapTuple ruletup, TupleDesc rulettc,
 		return;
 	}
 
-	query = (Query *) lfirst(actions);
+	query = (Query *) linitial(actions);
 
 	if (ev_type != '1' || ev_attr >= 0 || !is_instead ||
 		strcmp(ev_qual, "<>") != 0 || query->commandType != CMD_SELECT)
@@ -1670,7 +1673,7 @@ get_query_def(Query *query, StringInfo buf, List *parentnamespace,
 	deparse_namespace dpns;
 
 	context.buf = buf;
-	context.namespaces = lcons(&dpns, parentnamespace);
+	context.namespaces = lcons(&dpns, list_copy(parentnamespace));
 	context.varprefix = (parentnamespace != NIL ||
 						 length(query->rtable) != 1);
 	context.prettyFlags = prettyFlags;
@@ -1725,7 +1728,7 @@ get_select_query_def(Query *query, deparse_context *context,
 	StringInfo	buf = context->buf;
 	bool		force_colno;
 	char	   *sep;
-	List	   *l;
+	ListCell   *l;
 
 	/*
 	 * If the Query node has a setOperations tree, then it's the top level
@@ -1802,7 +1805,7 @@ get_basic_select_query(Query *query, deparse_context *context,
 {
 	StringInfo	buf = context->buf;
 	char	   *sep;
-	List	   *l;
+	ListCell   *l;
 	int			colno;
 
 	/*
@@ -2057,7 +2060,7 @@ get_insert_query_def(Query *query, deparse_context *context)
 	RangeTblEntry *select_rte = NULL;
 	RangeTblEntry *rte;
 	char	   *sep;
-	List	   *l;
+	ListCell   *l;
 
 	/*
 	 * If it's an INSERT ... SELECT there will be a single subquery RTE
@@ -2136,10 +2139,10 @@ get_insert_query_def(Query *query, deparse_context *context)
 static void
 get_update_query_def(Query *query, deparse_context *context)
 {
-	StringInfo	buf = context->buf;
-	char	   *sep;
-	RangeTblEntry *rte;
-	List	   *l;
+	StringInfo		 buf = context->buf;
+	char			*sep;
+	RangeTblEntry	*rte;
+	ListCell		*l;
 
 	/*
 	 * Start the query with UPDATE relname SET
@@ -2271,17 +2274,17 @@ static void
 get_names_for_var(Var *var, deparse_context *context,
 				  char **schemaname, char **refname, char **attname)
 {
-	List	   *nslist = context->namespaces;
+	ListCell   *nslist_item = list_head(context->namespaces);
 	int			sup = var->varlevelsup;
 	deparse_namespace *dpns;
 	RangeTblEntry *rte;
 
 	/* Find appropriate nesting depth */
-	while (sup-- > 0 && nslist != NIL)
-		nslist = lnext(nslist);
-	if (nslist == NIL)
+	while (sup-- > 0 && nslist_item != NULL)
+		nslist_item = lnext(nslist_item);
+	if (nslist_item == NULL)
 		elog(ERROR, "bogus varlevelsup: %d", var->varlevelsup);
-	dpns = (deparse_namespace *) lfirst(nslist);
+	dpns = (deparse_namespace *) lfirst(nslist_item);
 
 	/* Find the relevant RTE */
 	if (var->varno >= 1 && var->varno <= length(dpns->rtable))
@@ -2342,13 +2345,13 @@ get_names_for_var(Var *var, deparse_context *context,
 static RangeTblEntry *
 find_rte_by_refname(const char *refname, deparse_context *context)
 {
-	RangeTblEntry *result = NULL;
-	List	   *nslist;
+	RangeTblEntry  *result = NULL;
+	ListCell	   *nslist;
 
 	foreach(nslist, context->namespaces)
 	{
 		deparse_namespace *dpns = (deparse_namespace *) lfirst(nslist);
-		List	   *rtlist;
+		ListCell	   *rtlist;
 
 		foreach(rtlist, dpns->rtable)
 		{
@@ -2396,7 +2399,7 @@ get_simple_binary_op_name(OpExpr *expr)
 	if (length(args) == 2)
 	{
 		/* binary operator */
-		Node	   *arg1 = (Node *) lfirst(args);
+		Node	   *arg1 = (Node *) linitial(args);
 		Node	   *arg2 = (Node *) lsecond(args);
 		const char *op;
 
@@ -2501,7 +2504,7 @@ isSimpleNode(Node *node, Node *parentNode, int prettyFlags)
 					 * Operators are same priority --- can skip parens
 					 * only if we have (a - b) - c, not a - (b - c).
 					 */
-					if (node == (Node *) lfirst(((OpExpr *) parentNode)->args))
+					if (node == (Node *) linitial(((OpExpr *) parentNode)->args))
 						return true;
 
 					return false;
@@ -2759,8 +2762,8 @@ get_rule_expr(Node *node, deparse_context *context,
 				ArrayRef   *aref = (ArrayRef *) node;
 				bool		savevarprefix = context->varprefix;
 				bool		need_parens;
-				List	   *lowlist;
-				List	   *uplist;
+				ListCell   *lowlist_item;
+				ListCell   *uplist_item;
 
 				/*
 				 * If we are doing UPDATE array[n] = expr, we need to
@@ -2783,18 +2786,19 @@ get_rule_expr(Node *node, deparse_context *context,
 				if (need_parens)
 					appendStringInfoChar(buf, ')');
 				context->varprefix = savevarprefix;
-				lowlist = aref->reflowerindexpr;
-				foreach(uplist, aref->refupperindexpr)
+				lowlist_item = list_head(aref->reflowerindexpr);
+				foreach(uplist_item, aref->refupperindexpr)
 				{
 					appendStringInfo(buf, "[");
-					if (lowlist)
+					if (lowlist_item)
 					{
-						get_rule_expr((Node *) lfirst(lowlist), context,
+						get_rule_expr((Node *) lfirst(lowlist_item), context,
 									  false);
 						appendStringInfo(buf, ":");
-						lowlist = lnext(lowlist);
+						lowlist_item = lnext(lowlist_item);
 					}
-					get_rule_expr((Node *) lfirst(uplist), context, false);
+					get_rule_expr((Node *) lfirst(uplist_item),
+								  context, false);
 					appendStringInfo(buf, "]");
 				}
 				if (aref->refassgnexpr)
@@ -2818,7 +2822,7 @@ get_rule_expr(Node *node, deparse_context *context,
 			{
 				DistinctExpr *expr = (DistinctExpr *) node;
 				List	   *args = expr->args;
-				Node	   *arg1 = (Node *) lfirst(args);
+				Node	   *arg1 = (Node *) linitial(args);
 				Node	   *arg2 = (Node *) lsecond(args);
 
 				if (!PRETTY_PAREN(context))
@@ -2835,7 +2839,7 @@ get_rule_expr(Node *node, deparse_context *context,
 			{
 				ScalarArrayOpExpr *expr = (ScalarArrayOpExpr *) node;
 				List	   *args = expr->args;
-				Node	   *arg1 = (Node *) lfirst(args);
+				Node	   *arg1 = (Node *) linitial(args);
 				Node	   *arg2 = (Node *) lsecond(args);
 
 				if (!PRETTY_PAREN(context))
@@ -2856,20 +2860,22 @@ get_rule_expr(Node *node, deparse_context *context,
 		case T_BoolExpr:
 			{
 				BoolExpr   *expr = (BoolExpr *) node;
-				List	   *args = expr->args;
+				Node	   *first_arg = linitial(expr->args);
+				ListCell   *arg = lnext(list_head(expr->args));
 
 				switch (expr->boolop)
 				{
 					case AND_EXPR:
 						if (!PRETTY_PAREN(context))
 							appendStringInfoChar(buf, '(');
-						get_rule_expr_paren((Node *) lfirst(args), context,
+						get_rule_expr_paren(first_arg, context,
 											false, node);
-						while ((args = lnext(args)) != NIL)
+						while (arg)
 						{
 							appendStringInfo(buf, " AND ");
-							get_rule_expr_paren((Node *) lfirst(args), context,
+							get_rule_expr_paren((Node *) lfirst(arg), context,
 												false, node);
+							arg = lnext(arg);
 						}
 						if (!PRETTY_PAREN(context))
 							appendStringInfoChar(buf, ')');
@@ -2878,13 +2884,14 @@ get_rule_expr(Node *node, deparse_context *context,
 					case OR_EXPR:
 						if (!PRETTY_PAREN(context))
 							appendStringInfoChar(buf, '(');
-						get_rule_expr_paren((Node *) lfirst(args), context,
+						get_rule_expr_paren(first_arg, context,
 											false, node);
-						while ((args = lnext(args)) != NIL)
+						while (arg)
 						{
 							appendStringInfo(buf, " OR ");
-							get_rule_expr_paren((Node *) lfirst(args), context,
+							get_rule_expr_paren((Node *) lfirst(arg), context,
 												false, node);
+							arg = lnext(arg);
 						}
 						if (!PRETTY_PAREN(context))
 							appendStringInfoChar(buf, ')');
@@ -2894,7 +2901,7 @@ get_rule_expr(Node *node, deparse_context *context,
 						if (!PRETTY_PAREN(context))
 							appendStringInfoChar(buf, '(');
 						appendStringInfo(buf, "NOT ");
-						get_rule_expr_paren((Node *) lfirst(args), context,
+						get_rule_expr_paren(first_arg, context,
 											false, node);
 						if (!PRETTY_PAREN(context))
 							appendStringInfoChar(buf, ')');
@@ -2989,7 +2996,7 @@ get_rule_expr(Node *node, deparse_context *context,
 		case T_CaseExpr:
 			{
 				CaseExpr   *caseexpr = (CaseExpr *) node;
-				List	   *temp;
+				ListCell   *temp;
 
 				appendContextKeyword(context, "CASE",
 									 0, PRETTYINDENT_VAR, 0);
@@ -3035,7 +3042,7 @@ get_rule_expr(Node *node, deparse_context *context,
 		case T_ArrayExpr:
 			{
 				ArrayExpr  *arrayexpr = (ArrayExpr *) node;
-				List	   *element;
+				ListCell   *element;
 				char	   *sep;
 
 				appendStringInfo(buf, "ARRAY[");
@@ -3055,7 +3062,7 @@ get_rule_expr(Node *node, deparse_context *context,
 		case T_RowExpr:
 			{
 				RowExpr	   *rowexpr = (RowExpr *) node;
-				List	   *arg;
+				ListCell   *arg;
 				char	   *sep;
 
 				/*
@@ -3082,7 +3089,7 @@ get_rule_expr(Node *node, deparse_context *context,
 		case T_CoalesceExpr:
 			{
 				CoalesceExpr *coalesceexpr = (CoalesceExpr *) node;
-				List	   *arg;
+				ListCell   *arg;
 				char	   *sep;
 
 				appendStringInfo(buf, "COALESCE(");
@@ -3102,7 +3109,7 @@ get_rule_expr(Node *node, deparse_context *context,
 		case T_NullIfExpr:
 			{
 				NullIfExpr *nullifexpr = (NullIfExpr *) node;
-				List	   *arg;
+				ListCell   *arg;
 				char	   *sep;
 
 				appendStringInfo(buf, "NULLIF(");
@@ -3239,7 +3246,7 @@ get_oper_expr(OpExpr *expr, deparse_context *context)
 	if (length(args) == 2)
 	{
 		/* binary operator */
-		Node	   *arg1 = (Node *) lfirst(args);
+		Node	   *arg1 = (Node *) linitial(args);
 		Node	   *arg2 = (Node *) lsecond(args);
 
 		get_rule_expr_paren(arg1, context, true, (Node *) expr);
@@ -3252,7 +3259,7 @@ get_oper_expr(OpExpr *expr, deparse_context *context)
 	else
 	{
 		/* unary operator --- but which side? */
-		Node	   *arg = (Node *) lfirst(args);
+		Node	   *arg = (Node *) linitial(args);
 		HeapTuple	tp;
 		Form_pg_operator optup;
 
@@ -3298,7 +3305,7 @@ get_func_expr(FuncExpr *expr, deparse_context *context,
 	Oid			funcoid = expr->funcid;
 	Oid			argtypes[FUNC_MAX_ARGS];
 	int			nargs;
-	List	   *l;
+	ListCell   *l;
 	char	   *sep;
 
 	/*
@@ -3308,7 +3315,7 @@ get_func_expr(FuncExpr *expr, deparse_context *context,
 	 */
 	if (expr->funcformat == COERCE_IMPLICIT_CAST && !showimplicit)
 	{
-		get_rule_expr_paren((Node *) lfirst(expr->args), context,
+		get_rule_expr_paren((Node *) linitial(expr->args), context,
 							showimplicit, (Node *) expr);
 		return;
 	}
@@ -3320,7 +3327,7 @@ get_func_expr(FuncExpr *expr, deparse_context *context,
 	if (expr->funcformat == COERCE_EXPLICIT_CAST ||
 		expr->funcformat == COERCE_IMPLICIT_CAST)
 	{
-		Node	   *arg = lfirst(expr->args);
+		Node	   *arg = linitial(expr->args);
 		Oid			rettype = expr->funcresulttype;
 		int32		coercedTypmod;
 
@@ -3424,7 +3431,7 @@ strip_type_coercion(Node *expr, Oid resultType)
 		if (exprIsLengthCoercion(expr, NULL))
 			return expr;
 
-		return (Node *) lfirst(func->args);
+		return (Node *) linitial(func->args);
 	}
 
 	return expr;
@@ -3580,7 +3587,7 @@ get_sublink_expr(SubLink *sublink, deparse_context *context)
 {
 	StringInfo	buf = context->buf;
 	Query	   *query = (Query *) (sublink->subselect);
-	List	   *l;
+	ListCell   *l;
 	char	   *sep;
 	bool		need_paren;
 
@@ -3625,7 +3632,7 @@ get_sublink_expr(SubLink *sublink, deparse_context *context)
 
 		case ANY_SUBLINK:
 			if (length(sublink->operName) == 1 &&
-				strcmp(strVal(lfirst(sublink->operName)), "=") == 0)
+				strcmp(strVal(linitial(sublink->operName)), "=") == 0)
 			{
 				/* Represent = ANY as IN */
 				appendStringInfo(buf, "IN ");
@@ -3680,7 +3687,7 @@ get_from_clause(Query *query, deparse_context *context)
 {
 	StringInfo	buf = context->buf;
 	bool		first = true;
-	List	   *l;
+	ListCell   *l;
 
 	/*
 	 * We use the query's jointree as a guide to what to print.  However,
@@ -3763,12 +3770,12 @@ get_from_clause_item(Node *jtnode, Query *query, deparse_context *context)
 			gavealias = true;
 			if (rte->alias->colnames != NIL && coldeflist == NIL)
 			{
-				List	   *col;
+				ListCell   *col;
 
 				appendStringInfoChar(buf, '(');
 				foreach(col, rte->alias->colnames)
 				{
-					if (col != rte->alias->colnames)
+					if (col != list_head(rte->alias->colnames))
 						appendStringInfo(buf, ", ");
 					appendStringInfoString(buf,
 										   quote_identifier(strVal(lfirst(col))));
@@ -3897,12 +3904,12 @@ get_from_clause_item(Node *jtnode, Query *query, deparse_context *context)
 		{
 			if (j->using)
 			{
-				List	   *col;
+				ListCell   *col;
 
 				appendStringInfo(buf, " USING (");
 				foreach(col, j->using)
 				{
-					if (col != j->using)
+					if (col != list_head(j->using))
 						appendStringInfo(buf, ", ");
 					appendStringInfoString(buf,
 								quote_identifier(strVal(lfirst(col))));
@@ -3929,12 +3936,12 @@ get_from_clause_item(Node *jtnode, Query *query, deparse_context *context)
 							 quote_identifier(j->alias->aliasname));
 			if (j->alias->colnames != NIL)
 			{
-				List	   *col;
+				ListCell   *col;
 
 				appendStringInfoChar(buf, '(');
 				foreach(col, j->alias->colnames)
 				{
-					if (col != j->alias->colnames)
+					if (col != list_head(j->alias->colnames))
 						appendStringInfo(buf, ", ");
 					appendStringInfoString(buf,
 								  quote_identifier(strVal(lfirst(col))));
@@ -3958,7 +3965,7 @@ static void
 get_from_clause_coldeflist(List *coldeflist, deparse_context *context)
 {
 	StringInfo	buf = context->buf;
-	List	   *col;
+	ListCell   *col;
 	int			i = 0;
 
 	appendStringInfoChar(buf, '(');
@@ -4337,20 +4344,21 @@ generate_operator_name(Oid operid, Oid arg1, Oid arg2)
 static void
 print_operator_name(StringInfo buf, List *opname)
 {
-	int			nnames = length(opname);
+	ListCell	*op = list_head(opname);
+	int			 nnames = length(opname);
 
 	if (nnames == 1)
-		appendStringInfoString(buf, strVal(lfirst(opname)));
+		appendStringInfoString(buf, strVal(lfirst(op)));
 	else
 	{
 		appendStringInfo(buf, "OPERATOR(");
 		while (nnames-- > 1)
 		{
 			appendStringInfo(buf, "%s.",
-							 quote_identifier(strVal(lfirst(opname))));
-			opname = lnext(opname);
+							 quote_identifier(strVal(lfirst(op))));
+			op = lnext(op);
 		}
-		appendStringInfo(buf, "%s)", strVal(lfirst(opname)));
+		appendStringInfo(buf, "%s)", strVal(lfirst(op)));
 	}
 }